/*-------------------------------------------------------------------------
 *
 * linux.c
 *      Dynamic Loader for Postgres for Linux, generated from those for
 *      Ultrix.
 *
 *      You need to install the dld library on your Linux system!
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *      src/backend/port/dynloader/linux.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#ifdef HAVE_DLD_H
#include <dld.h>
#endif

#include "dynloader.h"
#include "miscadmin.h"


#ifndef HAVE_DLOPEN

void *
pg_dlopen(char *filename)
{
#ifndef HAVE_DLD_H
    elog(ERROR, "dynamic load not supported");
    return NULL;
#else
    static int    dl_initialized = 0;

    /*
     * initializes the dynamic loader with the executable's pathname. (only
     * needs to do this the first time pg_dlopen is called.)
     */
    if (!dl_initialized)
    {
        if (dld_init(dld_find_executable(my_exec_path)))
            return NULL;

        /*
         * if there are undefined symbols, we want dl to search from the
         * following libraries also.
         */
        dl_initialized = 1;
    }

    /*
     * link the file, then check for undefined symbols!
     */
    if (dld_link(filename))
        return NULL;

    /*
     * If undefined symbols: try to link with the C and math libraries! This
     * could be smarter, if the dynamic linker was able to handle shared libs!
     */
    if (dld_undefined_sym_count > 0)
    {
        if (dld_link("/usr/lib/libc.a"))
        {
            elog(WARNING, "could not link C library");
            return NULL;
        }
        if (dld_undefined_sym_count > 0)
        {
            if (dld_link("/usr/lib/libm.a"))
            {
                elog(WARNING, "could not link math library");
                return NULL;
            }
            if (dld_undefined_sym_count > 0)
            {
                int            count = dld_undefined_sym_count;
                char      **list = dld_list_undefined_sym();

                /* list the undefined symbols, if any */
                do
                {
                    elog(WARNING, "\"%s\" is undefined", *list);
                    list++;
                    count--;
                } while (count > 0);

                dld_unlink_by_file(filename, 1);
                return NULL;
            }
        }
    }

    return (void *) strdup(filename);
#endif
}

PGFunction
pg_dlsym(void *handle, char *funcname)
{
#ifndef HAVE_DLD_H
    return NULL;
#else
    return (PGFunction) dld_get_func((funcname));
#endif
}

void
pg_dlclose(void *handle)
{
#ifndef HAVE_DLD_H
#else
    dld_unlink_by_file(handle, 1);
    free(handle);
#endif
}

char *
pg_dlerror(void)
{
#ifndef HAVE_DLD_H
    return "dynaloader unsupported";
#else
    return dld_strerror(dld_errno);
#endif
}

#endif                            /* !HAVE_DLOPEN */
